This research was prompted by a field study performed at the
Celanese Corporation Wastewater Treatment Plant, Narrows, VA., in which
calcium chloride addition had improved sludge characteristics that were
believed to have deteriorated because of sodium hydroxide additions for
pH control.
Research objectives were to determine whether the observed
improvements during the full-scale plant study were caused by the
addition of divalent cations and whether the deterioration of the sludge
was due to sodium ion additions.
Bench-scale, activated sludge reactors were fed wastewater from the
Celanese plant to model plant conditions. Sodium was added in an
attempt to cause deterioration of the sludge characteristics. Magnesium
and calcium were used as divalent cations to try to improve the sludge
characteristics.
Results of the study indicated that the magnitude of the effects
seen in the full-scale plant study could not be reproduced in the
laboratory. Magnesium produced little or no effect on the system and
calcium improved the sludge characteristics slightly. Sodium caused
deterioration of the sludge but not as dramatically as the full-scale
study. This suggested that sodium alone did not adversely affect the
sludge but rather, sodium hydroxide might have been combined with
organics in the waste which then affected the system.
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